Roaming and signaling interworking are the keys to the success of Global System for Mobile Communication (GSM). The GSM association has more than 600 operator members. Network interworking between two operators is usually realized through a bilateral protocol. With the arrival of 3G times, services become more diversified and there are endless new access technologies. Thus, it becomes harder and harder to meet the requirements of members by realizing the network interworking through bilateral protocol. Also, the cost on establishing the bilateral protocol presents an obstacle to develop new roaming service by some operators.
The status report mechanism of the GSM network (called G network for short) is a short message sending process for improving the performance of G network. If the process that a Short Message Service Center (SMSC) sends a short message to a user is failed (for example, the mobile phone of the user is turned off), it consumes a large amount of network resources to ensure that the short message is successfully sent to the user terminal just by a retry mechanism of the SMSC. The principle of the notification mechanism is recording the user status flag, notifying the SMSC to cache the short message when the user is unreachable, and notifying the SMSC to send the short message when the user is reachable. The notification mechanism can greatly improve the performance of network, and is realized specifically by the following way.
The signaling involved in this mechanism comprises: status report (for example, Report Deliver Status (RDS)) signaling and notification signaling (for example, ALERT). When failing to send the Mobile Terminated (MT) short message, the SMSC sends the status report signaling to a Home Location Register (HLR) according to the failure condition to notify the HLR that the user is unreachable. After receiving the status report signaling, the HLR marks the user record to indicate the current status of user. When the user terminal can receive the short message once more (for example, after the user turns on the mobile phone), the HLR receives notification sent from a Visitor Location Register (VLR), and then transmits the notification signaling to the SMSC according to the user record to notify the SMSC that it can continue to send the stored short message.
However, when the user roams to other network or operator, the version of Multimedia Access Protocol (MAP) adopted by the current network or operator may be different from that adopted by the target network or operator. Thus, it is impossible to directly interact, and the current short message status notification mechanism cannot be realized.